The majority of pregnancies achieved by artificial insemination (AI) are singleton pregnancies according to the statistical report issued by the Spanish Fertility Society in 2018. This percentage is increasing every year. The explanation is based on the fact that AI treatments and their ovarian stimulation are increasingly controlled to avoid multiple pregnancies, which could endanger the health of the mother and the babies. Therefore, the aim of AI is to achieve the development of only one or two eggs. When there is a higher ovarian production, AI is cancelled in that cycle.
If we look at the twin birth rate in CAI, it is 10.9%, while in DAI it is 10%.